Move hub processing in debug info to a separate type

Author: dominikmascherbauer

substratevm/debug/gdbpy/gdb-debughelpers.py

@@ -108,7 +108,7 @@ class SVMUtil:
     string_type = gdb.lookup_type("java.lang.String")
     enum_type = gdb.lookup_type("java.lang.Enum")
     object_type = gdb.lookup_type("java.lang.Object")
-    hub_type = gdb.lookup_type("java.lang.Class")
+    hub_type = gdb.lookup_type("Encoded$Dynamic$Hub")
     null = gdb.Value(0).cast(object_type.pointer())
     classloader_type = gdb.lookup_type("java.lang.ClassLoader")
     wrapper_types = [gdb.lookup_type(f'java.lang.{x}') for x in
@@ -141,7 +141,7 @@ def get_uncompressed_type(cls, t: gdb.Type) -> gdb.Type:
         # compressed types only exist for java type which are either struct or union
         if t.code != gdb.TYPE_CODE_STRUCT and t.code != gdb.TYPE_CODE_UNION:
             return t
-        result = cls.get_base_class(t) if cls.is_compressed(t) else t
+        result = cls.get_base_class(t) if (cls.is_compressed(t) and t != cls.hub_type) else t
         trace(f'<SVMUtil> - get_uncompressed_type({t}) = {result}')
         return result
 
@@ -177,7 +177,7 @@ def get_compressed_oop(cls, obj: gdb.Value) -> int:
         # recreate compressed oop from the object address
         # this reverses the uncompress expression from
         # com.oracle.objectfile.elf.dwarf.DwarfInfoSectionImpl#writeIndirectOopConversionExpression
-        is_hub = cls.get_rtt(obj) == cls.hub_type
+        is_hub = cls.get_basic_type(obj.type) == cls.hub_type
         compression_shift = cls.compression_shift
         num_reserved_bits = int.bit_count(cls.reserved_bits_mask)
         num_alignment_bits = int.bit_count(cls.object_alignment - 1)
@@ -205,6 +205,11 @@ def get_unqualified_type_name(cls, qualified_type_name: str) -> str:
 
     @classmethod
     def is_compressed(cls, t: gdb.Type) -> bool:
+        # for the hub type we always want handle it as compressed as there is no clear distinction in debug info for
+        # the hub field, and it may always have an expression in the type's data_location attribute
+        if cls.get_basic_type(t) == cls.hub_type:
+            return True
+
         type_name = cls.get_basic_type(t).name
         if type_name is None:
             # fallback to the GDB type printer for t
@@ -363,6 +368,9 @@ def get_classloader_namespace(cls, obj: gdb.Value) -> str:
     def get_rtt(cls, obj: gdb.Value) -> gdb.Type:
         static_type = cls.get_basic_type(obj.type)
 
+        if static_type == cls.hub_type:
+            return cls.hub_type
+
         # check for interfaces and cast them to Object to make the hub accessible
         if cls.get_uncompressed_type(cls.get_basic_type(obj.type)).code == gdb.TYPE_CODE_UNION:
             obj = cls.cast_to(obj, cls.object_type)

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/debugentry/ClassEntry.java

@@ -288,8 +288,8 @@ protected MethodEntry processMethod(DebugMethodInfo debugMethodInfo, DebugInfoBa
     }
 
     @Override
-    protected FieldEntry addField(DebugFieldInfo debugFieldInfo, DebugInfoBase debugInfoBase, DebugContext debugContext) {
-        FieldEntry fieldEntry = super.addField(debugFieldInfo, debugInfoBase, debugContext);
+    protected FieldEntry createField(DebugFieldInfo debugFieldInfo, DebugInfoBase debugInfoBase, DebugContext debugContext) {
+        FieldEntry fieldEntry = super.createField(debugFieldInfo, debugInfoBase, debugContext);
         return fieldEntry;
     }
 

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/debugentry/DebugInfoBase.java

@@ -46,7 +46,6 @@
 import com.oracle.objectfile.debuginfo.DebugInfoProvider.DebugLocalValueInfo;
 import com.oracle.objectfile.debuginfo.DebugInfoProvider.DebugLocationInfo;
 import com.oracle.objectfile.debuginfo.DebugInfoProvider.DebugTypeInfo.DebugTypeKind;
-import com.oracle.objectfile.elf.dwarf.DwarfDebugInfo;
 
 import jdk.graal.compiler.debug.DebugContext;
 import jdk.vm.ci.meta.ResolvedJavaType;
@@ -135,6 +134,10 @@ public abstract class DebugInfoBase {
      * Handle on class entry for java.lang.Object.
      */
     private ClassEntry objectClass;
+    /**
+     * The type entry for java.lang.Class.
+     */
+    private ClassEntry classClass;
     /**
      * List of all top level compiled methods found in debug info. These ought to arrive via the
      * debug info API in ascending address range order.
@@ -202,11 +205,6 @@ public abstract class DebugInfoBase {
      */
     private int compiledCodeMax;
 
-    /**
-     * The type entry for java.lang.Class.
-     */
-    private ClassEntry hubClassEntry;
-
     @SuppressWarnings("this-escape")
     public DebugInfoBase(ByteOrder byteOrder) {
         this.byteOrder = byteOrder;
@@ -218,7 +216,6 @@ public DebugInfoBase(ByteOrder byteOrder) {
         this.pointerSize = 0;
         this.objectAlignment = 0;
         this.numAlignmentBits = 0;
-        this.hubClassEntry = null;
         this.compiledCodeMax = 0;
         // create and index an empty dir with index 0.
         ensureDirEntry(EMPTY_PATH);
@@ -372,9 +369,6 @@ private TypeEntry createTypeEntry(String typeName, String fileName, Path filePat
             case INSTANCE: {
                 FileEntry fileEntry = addFileEntry(fileName, filePath);
                 typeEntry = new ClassEntry(typeName, fileEntry, size);
-                if (typeEntry.getTypeName().equals(DwarfDebugInfo.HUB_TYPE_NAME)) {
-                    hubClassEntry = (ClassEntry) typeEntry;
-                }
                 break;
             }
             case INTERFACE: {
@@ -423,6 +417,9 @@ private TypeEntry addTypeEntry(ResolvedJavaType idType, String typeName, String
             if (idType == null) {
                 headerType = (HeaderTypeEntry) typeEntry;
             }
+            if (typeName.equals("java.lang.Class")) {
+                classClass = (ClassEntry) typeEntry;
+            }
             if (typeName.equals("java.lang.Object")) {
                 objectClass = (ClassEntry) typeEntry;
             }
@@ -479,6 +476,12 @@ public ClassEntry lookupObjectClass() {
         return objectClass;
     }
 
+    public ClassEntry lookupClassClass() {
+        // this should only be looked up after all types have been notified
+        assert classClass != null;
+        return classClass;
+    }
+
     private void addPrimaryRange(PrimaryRange primaryRange, DebugCodeInfo debugCodeInfo, ClassEntry classEntry) {
         CompiledMethodEntry compiledMethod = classEntry.indexPrimary(primaryRange, debugCodeInfo.getFrameSizeChanges(), debugCodeInfo.getFrameSize());
         indexCompiledMethod(compiledMethod);
@@ -737,14 +740,6 @@ public String getCachePath() {
         return cachePath;
     }
 
-    public boolean isHubClassEntry(StructureTypeEntry typeEntry) {
-        return typeEntry.getTypeName().equals(DwarfDebugInfo.HUB_TYPE_NAME);
-    }
-
-    public ClassEntry getHubClassEntry() {
-        return hubClassEntry;
-    }
-
     private static void collectFilesAndDirs(ClassEntry classEntry) {
         // track files and dirs we have already seen so that we only add them once
         EconomicSet<FileEntry> visitedFiles = EconomicSet.create();

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/debugentry/HeaderTypeEntry.java

@@ -34,10 +34,16 @@
 
 public class HeaderTypeEntry extends StructureTypeEntry {
 
+    FieldEntry hubField;
+
     public HeaderTypeEntry(String typeName, int size) {
         super(typeName, size);
     }
 
+    public FieldEntry getHubField() {
+        return hubField;
+    }
+
     @Override
     public DebugTypeKind typeKind() {
         return DebugTypeKind.HEADER;
@@ -49,5 +55,6 @@ public void addDebugInfo(DebugInfoBase debugInfoBase, DebugTypeInfo debugTypeInf
         assert debugTypeInfo.typeName().equals(typeName);
         DebugHeaderTypeInfo debugHeaderTypeInfo = (DebugHeaderTypeInfo) debugTypeInfo;
         debugHeaderTypeInfo.fieldInfoProvider().forEach(debugFieldInfo -> this.processField(debugFieldInfo, debugInfoBase, debugContext));
+        hubField = createField(debugHeaderTypeInfo.hubField(), debugInfoBase, debugContext);
     }
 }

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/debugentry/StructureTypeEntry.java

@@ -75,10 +75,11 @@ public int fieldCount() {
 
     protected void processField(DebugFieldInfo debugFieldInfo, DebugInfoBase debugInfoBase, DebugContext debugContext) {
         /* Delegate this so superclasses can override this and inspect the computed FieldEntry. */
-        addField(debugFieldInfo, debugInfoBase, debugContext);
+        FieldEntry fieldEntry = createField(debugFieldInfo, debugInfoBase, debugContext);
+        fields.add(fieldEntry);
     }
 
-    protected FieldEntry addField(DebugFieldInfo debugFieldInfo, DebugInfoBase debugInfoBase, DebugContext debugContext) {
+    protected FieldEntry createField(DebugFieldInfo debugFieldInfo, DebugInfoBase debugInfoBase, DebugContext debugContext) {
         String fieldName = debugInfoBase.uniqueDebugString(debugFieldInfo.name());
         ResolvedJavaType valueType = debugFieldInfo.valueType();
         String valueTypeName = valueType.toJavaName();
@@ -96,9 +97,7 @@ protected FieldEntry addField(DebugFieldInfo debugFieldInfo, DebugInfoBase debug
          * substitution
          */
         FileEntry fileEntry = debugInfoBase.ensureFileEntry(debugFieldInfo);
-        FieldEntry fieldEntry = new FieldEntry(fileEntry, fieldName, this, valueTypeEntry, fieldSize, fieldoffset, fieldIsEmbedded, fieldModifiers);
-        fields.add(fieldEntry);
-        return fieldEntry;
+        return new FieldEntry(fileEntry, fieldName, this, valueTypeEntry, fieldSize, fieldoffset, fieldIsEmbedded, fieldModifiers);
     }
 
     String memberModifiers(int modifiers) {

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/debuginfo/DebugInfoProvider.java

@@ -219,6 +219,8 @@ interface DebugPrimitiveTypeInfo extends DebugTypeInfo {
     interface DebugHeaderTypeInfo extends DebugTypeInfo {
 
         Stream<DebugFieldInfo> fieldInfoProvider();
+
+        DebugFieldInfo hubField();
     }
 
     interface DebugMemberInfo extends DebugFileInfo {

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/elf/dwarf/DwarfAbbrevSectionImpl.java

@@ -956,10 +956,11 @@ public int writeAbbrevs(DebugContext context, byte[] buffer, int p) {
          *
          * if address rebasing is not required then a data_location attribute on the layout type
          * will ensure that address tag bits are removed.
+         *
+         * The compressed layout is also used for representing the decode step for dynamic hubs.
+         * I.e. this is also required for builds without isolates
          */
-        if (dwarfSections.useHeapBase()) {
-            pos = writeCompressedLayoutAbbrev(context, buffer, pos);
-        }
+        pos = writeCompressedLayoutAbbrev(context, buffer, pos);
 
         pos = writeParameterDeclarationAbbrevs(context, buffer, pos);
         pos = writeLocalDeclarationAbbrevs(context, buffer, pos);
@@ -1116,9 +1117,6 @@ private int writeClassLayoutAbbrevs(@SuppressWarnings("unused") DebugContext con
         pos = writeClassLayoutAbbrev(context, AbbrevCode.CLASS_LAYOUT_TU, buffer, pos);
         pos = writeClassLayoutAbbrev(context, AbbrevCode.CLASS_LAYOUT_CU, buffer, pos);
         pos = writeClassLayoutAbbrev(context, AbbrevCode.CLASS_LAYOUT_ARRAY, buffer, pos);
-        if (!dwarfSections.useHeapBase()) {
-            pos = writeClassLayoutAbbrev(context, AbbrevCode.CLASS_LAYOUT_TU_2, buffer, pos);
-        }
         return pos;
     }
 
@@ -1147,10 +1145,6 @@ private int writeClassLayoutAbbrev(@SuppressWarnings("unused") DebugContext cont
         } else {
             pos = writeAttrType(DwarfAttribute.DW_AT_byte_size, buffer, pos);
             pos = writeAttrForm(DwarfForm.DW_FORM_data2, buffer, pos);
-            if (abbrevCode == AbbrevCode.CLASS_LAYOUT_TU_2) {
-                pos = writeAttrType(DwarfAttribute.DW_AT_data_location, buffer, pos);
-                pos = writeAttrForm(DwarfForm.DW_FORM_expr_loc, buffer, pos);
-            }
         }
         /*
          * Now terminate.

substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/elf/dwarf/DwarfDebugInfo.java

@@ -68,9 +68,8 @@ enum AbbrevCode {
         CLASS_CONSTANT,
         NAMESPACE,
         CLASS_LAYOUT_TU,
-        CLASS_LAYOUT_TU_2,
-        CLASS_LAYOUT_ARRAY,
         CLASS_LAYOUT_CU,
+        CLASS_LAYOUT_ARRAY,
         TYPE_POINTER_SIG,
         TYPE_POINTER,
         FOREIGN_TYPEDEF,
@@ -140,7 +139,7 @@ enum AbbrevCode {
      * The name of the type for header field hub which needs special case processing to remove tag
      * bits
      */
-    public static final String HUB_TYPE_NAME = "java.lang.Class";
+    public static final String HUB_TYPE_NAME = "Encoded$Dynamic$Hub";
     /* Full byte/word values. */
     private final DwarfStrSectionImpl dwarfStrSection;
     private final DwarfAbbrevSectionImpl dwarfAbbrevSection;